Recently, a static latent image developing method is mostly applied in an image forming apparatus for rapidly forming a high quality image. One of the important themes in this field is further improvement of the image quality. Many technological developments have been carried to the present time.
The most effective means for improving image quality is to reduce the diameter of the toner particles. The improvement in image quality has progressed by the use of toner particles having a smaller diameter and narrower distribution range than usual toner for the reason mentioned later.
For example, toner having a number average particle diameter of from 3.0 to 6.5 μm has recently been employed, although a toner having a number average diameter of from 9 to 11 μm has usually been used though the objective of the toner is to form high quality images.
In such cases, roughing of image is caused by the presence of coarse particles and scattering of the extremely fine particles are occurs when distribution of the toner particle diameter is broad. Consequently, efforts have been made to make the diameter uniform and the appearance of the toner particles since such the phenomena causes the degradation of image quality and environmental problems.